8 Responses. > 1  the Moon takes an elliptical path around the Earth. The planets make nearly elliptical orbits around the Sun, close enough for reasonable approximations, but the Moonâs Orbit around the Earth is sufficiently influenced by the Sun that it follows a path detectably different from an ellipse.
Quick Answer. In 1896, French scientist Antoine Henri Becquerel discovered radioactivity which was an early contribution to atomic theory. He discovered this phenomenon while experimenting with uranium and a photographic plate. Continue Reading.
Bohr began to work on the problem of the atom's structure. Ernest Rutherford had recently suggested the atom had a miniature, dense nucleus surrounded by a cloud of nearly weightless electrons. There were a few problems with the model, however. For example, according to classical physics, the electrons orbiting the nucleus should lose energy until they spiral down into the center, collapsing the atom. Bohr proposed adding to the model the new idea of quanta put forth by Max Planck in 1901.